1. Field of the Invention
The invention relates to a glow plug with a hollow body in which a ceramic heating rod with a sintered-in heating element is located, which projects axially on one side of the hollow body and which has a heating element which is connected to power supply terminals.
2. Description of Related Art
Glow plugs of the initially mentioned type are known which have a ceramic conductor and a metal resistance spiral as the heating element (German Patent Application Nos. 42 03 183 A1 and 41 33 046 A1).
Glow plugs are generally used as a starting aid in diesel engines and alcohol-fueled engines, for ignition of accessory heating plants, for igniting gas burners, etc.
In German Patent Application No. 42 03 183 A1, the ceramic conductor of the disclosed glow plugs consists of a conductor piece that is U-shaped and which is located in the front end of the projecting part of the heating element and forms a first heating element. This first heating element is connected to the power supply terminals via a second heating element in the form of a spiral made of metallic material.
The glow plug of German Patent Application No. 41 33 046 A1 has the heating spiral is connected directly to the power supply terminals.
Based on the bonding provided in glow plugs of this type in the heating area, especially between the first and the second heating elements, and between the second heating element and the power supply terminals, the process by which these glow plugs are produced is very complicated. Due to the necessary bonding in the heating area, them is, moreover, a thermal loading limit of the ceramic conductor sintered into the ceramic insulator is roughly 1200.degree. C.